Comparison of histological features in early spontaneous and induced trisomic abortions.

Qualitative and quantitative histological features of a series of induced (n = 6) and spontaneous (n = 24) trisomic abortions were compared. The chorionic villi of induced abortions were large and of irregular contour. The stroma contained many blood vessels and did not show fibrohyalinic change. The intact trophoblast demonstrated 'hyperplasia'. Contrastingly, spontaneous abortions were composed of smaller villi with somewhat more fibrohyalinic stroma containing a few blood vessels. The trophoblast did not show 'hyperplasia'. However, many syncytial knots were present. Although some of histological features were shown to relate to gestational age, which could not be completely matched for, it was unlikely that this could account for the observed differences. Analysis restricted to induced and spontaneous abortions of comparable gestational age demonstrated the same differences. The time-lag between first blood loss and final gestational loss in spontaneous abortions did not appear to be of influence on any of the variables. The striking histopathological differences between induced and spontaneous abortions are mainly considered to be due to cessation of circulation at some time and to disintegration of trophoblast as a result of ischaemia in spontaneous abortions.